if a line is equally inclined to axes ,prove that its slope is +_1

The inclination of the line with x and y axes be $\alpha \& \beta$
respectively.

If the line is equally inclined with the axes, then $$\begin{gathered} \alpha =\beta \\ \Rightarrow \alpha +\beta =2\alpha \\ \Rightarrow \pm 90°=2\alpha \left(\because angle between the axes is \pm 90°\right) \\ \Rightarrow \pm 45°=\alpha \end{gathered}$$
Now,
Slope = $\tan \alpha =\tan \left(\pm 45°\right)=\pm 1$